Weird alright. We've grown various species of sweet potatoes for years and never seen anything like that before. Does it have seeds inside?
How strange! It is clearly attached to the sweet potato plant so I guess it is a sweet potato fruit. I have seen them flowering before, but never the fruit. Thanks for sharing :)
Oh I see. Quite strange. Sorry I have no idea.
Looking at the new photo it looks like a nagoora burr but bigger than normal. When you break a leaf or stem does it have a really peculiar smell?
I have been asked by our new member Leigh Burnett to tell you that it is Datura metel, or otherwise known as devil's apple or thorn apple. All parts are poisonous so don't let animals, chooks or people eat them (it could be fatal). Google Datura metel for more info.
Thanks Leigh and Lyn. It does have a really peculiar smell. I shall carefully dig it up and dispose of it. The seed must have been dropped by a bird, I guess.